1. Field of the Invention
The present invention relates to a visible light multiplex communication system, and more particularly, to a visible light multiplex communication system in which identification (ID) information and data information can be simultaneously transmitted and received to and from a server and a plurality of clients by using visible light.
2. Description of the Related Art
A visible light communication system uses visible light having a wavelength of about 380 nm to 780 nm that can be seen by the naked eye. As light-emitting diodes (LEDs) have drawn attention as a next generation illumination that replaces a general fluorescent lamp or incandescent lamp, visible light communication using LEDs starts to be used. Examples of light-emitting bodies that can be used in visible light communication include laser diodes (LDs) and LEDs.
A type of optical communication that is similar to visible light communication is infrared ray communication using infrared rays. However, since infrared rays cannot be seen by the naked eye, it is difficult to easily recognize the location of a light source. Furthermore, an infrared ray infrastructure has not been constituted, and infrared rays may affect human eyes adversely.
In addition, in a radio frequency (RF) method that is widely used as a wireless communication method, data can be easily transmitted from a device through an obstacle over a long distance. However, it is not easy to use the RF method only in a restricted space, and there is a large probability that interference occurs in aircrafts, medical devices, and the like and a device may malfunction.
Visible light communication may include visible light identification (ID) communication and visible light data communication according to the purpose of use.
The difference between visible light ID communication and visible light data communication is the purpose of use. In visible light ID communication, a unique ID is allocated to each visible light ID client and is used to manage many ID clients and to read and update information about IDs of the ID clients. An ID allocated to each ID client may be mapped to information of a server, like in a tag ID in radio frequency identification (RFID). In other words, detailed information mapped to an ID of a specific ID client may be stored in the server, and a user may call the detailed information from the server and may obtain the detailed information. On the other hands, in visible light data communication, various types of data, such as voice, images, texts, and the like, are transmitted and received in a simplex or duplex communication manner.
FIG. 1 illustrates a visible light data communication system according to the related art. A visible light data access point (AP) 3 that provides a visible light data communication service includes one or a plurality of LEDs 4 that emit visible light. A visible light data client 5 transmits and receives information to and from the visible light data AP 3 in a duplex communication manner. The visible light data AP 3 may transmit data information to the visible light data client 5 and may receive the data information from a server 1 connected to a network 2 and may also transmit the data information to the visible light data client 5.
FIG. 2 is a view of a visible light ID communication system according to the related art. A visible light ID collector 8 includes one or a plurality of LEDs 9 that emit visible light. A visible light tag client 10 receives a command from the visible light ID collector 8 and transmits an ID value to the visible light ID collector 8. The visible light ID collector 8 obtains information mapped to a visible light ID from a server 6 connected to a network 7.
However, the visible light data AP 3 illustrated in FIG. 1 and the visible light ID collector 8 illustrated in FIG. 2 generally use different protocols and have different hardware configurations. Thus, in order to provide a visible light data communication service and a visible light ID communication service in the same place, the visible light data AP 3 of FIG. 1 and the visible light ID collector 8 of FIG. 2, respectively, need to be installed. In addition, the visible light data AP 3 of FIG. 1 and the visible light ID collector 8 of FIG. 2 should be separated from each other by a sufficient distance so that they do not interfere with each other. Thus, in a general visible light communication system, when visible light ID communication and visible light data communication are simultaneously used, interference therebetween occur, and visible light ID communication and visible light data communication cannot be used in the same place.
In addition, general visible light communication methods mainly relate to one-to-one communication methods. Since a specific method of simultaneously performing communication between an AP 3 connected to a server 1 and a plurality of clients 5, 10 by using visible light has not been developed, a visible light multiplex communication system that satisfies this need is necessary.